Porous Matrix Sound Suppressor

ABSTRACT

Disclosed is a sound-suppressing device that employs a porous micro-channel diffusion matrix surrounding a hollow core lube that acts to increase the surface area of the suppressor and allow combustion gasses to diffuse and exit the suppressor. Various polymers can fee used to produce the porous micro-channel diffusion matrices. These porous polymer micro-channel diffusion matrices are made by sintering processes. By controlling the polymer type and particle size distribution of the particles that are sintered to create the porous polymer micro-channel diffusion matrix, the suppression can be maximized.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application claiming priority to non-provisional U.S. application Ser. No. 14/572300 filed on Dec. 16, 2014 which is entitled to the benefit of U.S. provisional application No. 62/009,732 filed on Jun. 9, 2014. The disclosures of the aforementioned applications are incorporated by reference in their entireties in the present application.

FIELD OF INVENTION

Disclosed is a sound-suppressing device for reducing the magnitude of perceived sound that occurs during the discharge of a firearm. Specifically, it pertains to a device that employs a porous micro-channel diffusion polymer matrix surrounding a hollow core tube, interposed between a distal containment cap and a proximal muzzle connection cap.

BACKGROUND OF INVENTION

Sound generation occurs when discharging a firearm. The sound heard is due to the following sources: the ignition of the cartridge; the discharge of propellant gas from the end of the barrel of a firearm, the flight of the bullet, the bullet impacting its target and the mechanical operation of the firearm itself. Multiple technologies can be employed to reduce the perceived sound associated with discharging a firearm. Typically, a suppressor (commonly known as a “silencer”) is capable of reducing some of the sound emitted from discharging a firearm.

Previous suppressors generally take the form of a cylindrically shaped metal tube with various internal mechanisms to reduce the sound of a discharge. These suppressors are typically made of metal (e.g. steel, aluminum, or titanium) that can withstand the heat and pressure associated with escaping propellant gasses. These previous suppressor designs utilize battling of all shapes and sizes to trap, cool, and decompress gasses released by a firearm in a controllable manner. The baffling design reduces the energy of the gasses, and when the gasses exit the suppressor, the perceived audible signature of the weapon is significantly reduced. Some examples include U.S. Pat. No. 8,579,075, U.S. Pat. No. 8,104,570, and U.S. Pat. No. 6,079,311.

Traditional suppressor designs have drawbacks that make them undesirable or inconvenient for some users. Drawbacks of these traditional suppressors may include but are not hunted to: altering the point of the bullet's impact on the target; adding significant weight to the firearm; increasing the blow back; having increased difficulties and increased costs associated with manufacturing intricate designs; changing the recoil of the firearm; increasing the barrel temperature of the firearm which gives the user a perceived mirage effect and decreases the effectiveness of suppressor, and difficulty in cleaning.

SUMMARY

This disclosure is directed to suppression devices that employ a porous polymer micro-channel diffusion matrix surrounding the outer surface of a hollow core tube, replacing the traditional inner baffling, to diffuse, slow and cool gasses released from the discharge of a firearm; reducing the audible signature. Herein are disclosed various porous polymer micro-channel diffusion matrices that maximize suppression. These porous polymer micro-channel diffusion matrices are made by sintering processes. By controlling the polymer type and particle size distribution of the particles that are sintered to create the porous micro-channel diffusion polymer matrix, the suppression can be maximized.

As a bullet passes through the hollow core tube, propellant gasses are released though the vents of the hollow core tube into the porous micro-channel diffusion polymer matrix where the gasses are diffused, slowed, and cooled. The porous micro-channel diffusion polymer matrix is interposed between containment caps. At the distal end (with respect to the firearm's muzzle) is a containment cap and at the proximal end is a muzzle connection cap that connects the device to the end of the firearm barrel. The suppression device disclosed effectively reduces the audible signature associated with the discharge of a firearm as well as reducing the flash associated with the release of combustion gasses out of the muzzle.

A suppressor with a porous micro-channel diffusion polymer matrix has advantages in that that it:

(a) reduces the muzzle Hash and the audible sound (−20 to −40 dB) associated with the discharge of a firearm that mitigates the need for ear protection; (b) does not substantially increase the overall weight of the firearm; the suppressor in the current application has a weight of only 3-4 ounces as compared to 10-15 ounces for previous suppressors; (c) substantially reduces the operating temperature of the surface of the suppressor and the firearm barrel, reducing the mirage effect and potentially increasing the lifetime of the barrel because only thermal resistant materials are used;

SHORT DESCRIPTION OF THE FIGURES

FIG. 1: A bisectional view of an embodiment of the suppressor device.

FIG. 2a : A containment cap view of the device shown in FIG. 1.

FIG. 2b : A muzzle cap view of the device shown in FIG. 1.

FIG. 3a : shows an exploded view of the device showing the hollow core tube, the porous micro-channel diffusion polymer matrix, and the sheath as individual parts.

FIG. 3b shows a partially assembled view of the device.

FIG. 4 shows a magnified image of a polycarbonate porous micro-channel diffusion polymer matrix highlighting pore sixe distribution.

FIG. 5 shows a magnified image of a polypropylene porous micro-channel diffusion polymer matrix highlighting pore size distribution.

DETAILED DESCRIPTION

Firearm suppressors are used to reduce the muzzle flash and the audible sound associated with the discharge of a firearm. However traditional suppressors .also have negative effects. Most suppressors change the point of impact; add significant weight, to the firearm; increase the blow back; change the recoil; increase the barrel temperature resulting in the perceived mirage effect and decreasing the effectiveness and shorted barrel lifetime, and are difficult to clean. Traditional suppressors also have complex designs such as inner baffling. The intricate designs of traditional suppressors increase their cost of manufacturing. The embodiments disclosed here minimize these negative effects.

The micro-channel design having-pores being fluidly connected to one another to form a network of exhaust flow passages that extend throughout the longitudinal axis of the matrix from the front end portion to the rear end portion acts as an outer diffusion baffle system which increases the surface area of the suppressor device and allows combustion gasses to diffuse through the polymer matrix. The matrix is also comprised of an interior surface and an exterior surface extending generally along the longitudinal axis with the interior surface defining an internal passage for receiving a projectile or for receiving a hollow core tube within the matrix. Having an outer porous micro-channel diffusion polymer matrix allows for the use of a “hollow core tube” within its interior surface, rather the traditional core tube comprised of a series of inner baffles forming a central aperture that allows for passage of the bullet. The vented lightweight hollow core is feasible because the porous micro-channel diffusion polymer matrix acts as the baffle system along the outer, rather than the inner, surface of the device.

FIGS. 1-3 show an embodiment of the suppressor device. Device 16 is comprised of a hollow core tube 5 surrounded along a longitudinal axis by a porous micro-channel diffusion polymer matrix 1. The hollow core tube is comprised of solid structure 12, preferably made out a thermally resistant metal, and a plurality of vents 13 forming a bore 11 that allows passage of a projectile through the suppressor. Though the vents 13 are shown as hexagonal in shape; the vents may be any shape feasible by manufacturing processes. Both ends of the hollow core tube 5 are threaded. Proximal end threads 7 connect the hollow tube 5 to the muzzle connection cap 3 via connection cap threads 10. Distal threads 8 connect the hollow tube 5 to the containment cap 2. Muzzle connection cap 3 located on a rear end portion of hollow core tube 5 is comprised of threaded passage 6 for attaching device 16 to a muzzle of a firearm. The muzzle connection cap 3 may be formed as a separate piece of a suitable material such as metal, as shown. However, the muzzle connection cap 3 may be formed as one piece of material with the diffusion matrix 1 within the scope of the present invention and be broadly defined as a muzzle connector. Connection cap 2 located on a front end portion of the hollow core tube 5 is comprised internally of threaded section 9 that interacts with distal threads 8 to join the connection cap 2 to the hollow core tube 5. The hollow core tube design is also not limited, to the design shown any feasible design with a solid structure wall and at least one vent hole extending radially through the wall is contemplated. Optionally the porous micro-channel diffusion polymer matrix 1 of device 16 is covered by sheath 4 which is press fit to the device via proximal recesses 15 in the muzzle connection cap 3 and distal recesses 14 in containment cap 2. Preferably the sheath 4 has a tubular shape, with an inner diameter that aligns with the outer diameter of the porous micro-channel diffusion polymer matrix and an outer diameter that is aligned with the outer diameter of both the muzzle connection cap and containment cap. The sheath extends from a rear end portion sealingly engaging the muzzle connector to a front end portion sealingly engaging the containment cap. The sheath can be solid or porous and may be comprised of carbon fiber, metal, or silicone rubber.

FIG. 4 shows a 35× magnified image of a section of polycarbonate porous micro-channel diffusion polymer matrix comprised of sintered polycarbonate particles 17, which form the physical structure of the matrix. The sintered particles 17 are arranged to define an interconnected network of pores 18. The illustrated pores 18 have a pore size distribution range from 90.71 μm to 340 μm. FIG. 5 shows a 35× magnified image of a section of polypropylene porous micro-channel diffusion polymer matrix comprised of sintered polypropylene particles 19 which define a network of pores 20. The illustrated pores 20 have a pore size distribution range from 87.93 micron to 383.4 μm. These images are for illustration purposes and are not meant to be limiting. The porous micro-channel diffusion polymer matrices depicted in FIGS. 4 and 5 were manufactured using particles between 100 μm and 3000 μm in diameter.

Embodiments of the disclosed device use porous polymer micro-channel diffusion matrices comprised of various types of polymers. Polymers are preferred because in general they are not good thermal conductors, having a thermal conductivity typically less than 1 W/mK. It is undesirable for heat to be absorbed because it has been found that heat reduces the efficiency of sound suppression in conventional suppressors. The suppressor device disclosed effectuates sound suppression by diffusing the gasses that are released when discharging a firearm. These released gasses bounce around within the porous polymer micro-channel diffusion matrix until they have lost their energy. Hence suppression is achieved without propagating the negative effects of heat. The use of polymers also reduces heat transfer through the suppressor into the barrel of the firearm which is also undesirable. Surprisingly, porous polymer micro-channel diffusion matrices comprised of polymers allow for effective sound suppression even when the porosity is lower. A lower porosity slows the gasses down, without the use of thermal transfer.

The particle size of the polymer that is used to manufacture the sintered porous polymer micro-channel diffusion matrix can ultimately determine the capability of the device to suppress sound. Generally, when sintered together, smaller particles create a porous polymer micro-channel diffusion matrix with smaller pores and higher surface area, whereas larger particles create a porous polymer micro-channel diffusion matrix with larger pores and lower surface area. Similarly if more particles of a given size distribution are packed into a sintering mold of a given volume, the size of the pores in the diffusion matrix is reduced and the surface area is increased. It is believed that a porous polymer micro-channel diffusion matrix with smaller pores and a higher surface area results in higher back pressure, which diffuses, slows, and cools the pressurized gases of the firearm discharge, which in turn provides a more effective suppression. Back pressure refers to pressure opposed, to the desired flow of a fluid in a confined place. This results in sound suppression, which can be measured using a sound meter (Larson Davis SoundTrack LXT) and compared with sound levels of on suppressed fire.

To produce a porous polymer micro-channel diffusion matrix with the desired characteristics requires sintering polymer particles of a particular size range while maintaining partial separation between the particles during sintering so as to form pores between adjacent particles that ultimately will be fluidly connected to one another to form a network of exhaust passages extending throughout the porous micro-channel diffusion polymer matrix. The internal passage of the porous micro-channel may be formed simultaneously as well. There are many industry standards which can be used to determine the particle size of the loose particulate that is sintered to form the porous microchannel diffusion matrix. ASTM D691.3-04(2009) is a standard for measuring the particle size diameter distribution of soil, but it can be used as the standard for determining the particle size diameter of other granular particles that will not reduce in size through vibration. Sieves of various sizes are used to separate particles by their diameter. Each gradation of particle diameter is weighed, and the weights are used to describe particle size distribution. A polymer particle size distribution in which 90% of the particles are between 100 and 3000 μm in diameter can be sintered to form a porous microchannel diffusion matrix that provides effective suppression. More effective suppression can be obtained by sintering the porous microchannel diffusion matrix from particles having a particle size distribution in which 90% of the particles are between 100 and 1000 μm in diameter. Still more effective suppression can be obtained by sintering the porous microchannel diffusion matrix from particles having a particle size distribution in which 90% of the particles are between 100 and 450 μm in diameter. The following sound suppression data was collected using polycarbonate porous micro-channel diffusion polymer matrices that were manufactured using individual sets of particles that corresponded to one of the three specific size ranges. The testing was performed with a .22 caliber pistol in outdoor conditions with no wind using subsonic .22 caliber rounds. The level of sound suppression achieved (i.e. the decrease In decibels measured) is comparable to conventional commercially available suppressors. Table 1 is for illustrative purposes only and not meant to be limiting.

TABLE 1 Sound Suppression Results Average Average Particle Particle Baseline Diameter Diameter Average Particle Trial (Unsuppressed) 2500 μm 800 μm Diameter 300 μm 1 153.5 134.2 128.3 126.2 2 154.3 133.4 128.1 126.8 3 154.3 133.0 127.9 125.9 4 153.7 132.7 126.7 126.0 5 154.1 133.5 128.3 126.2 6 153.9 133.0 128.0 125.5 7 154.2 133.4 128.3 125.9 8 154.2 133.8 129.5 124.7 9 154.1 133.7 129.5 125.5 10  154.6 133.7 129.6 125.7 Average 154.1 133.4 128.4 125.8 Sound Level (dB) Δ — −20.7 −25.7 −28.3

Any polymer that has a fractional melt can be sintered by a combination of pressure and/or heat. The viscosity of the polymer during the fractional melt is typically defined by its melt flow rate. Melt flow rate can be measured according to the technique described by ASTM D 1238. A melt flow rate less than 5 g/10 minutes is preferable for sintering because the polymer will have a viscosity that will bind the particles together while maintaining a porous structure. At melt flow rates higher than 5 g/10 minutes the polymer will liquefy, which is more suitable to injection molding or compression molding applications. More preferably, a melt flow rate less than 3 g/10 minutes will allow for a porous polymer micro-channel diffusion matrix to be manufactured with a reduced amount of meltback. Meltback is defined as a reduction in porosity and volume as a result of liquidation of the polymer, which would reduce the volume of the porous polymer micro-channel diffusion matrix in an irregular fashion; though it would it would still be porous. Most preferably, a melt flow rate less than 1 g/10 minutes will greatly minimize meltback.

Polymers that work particularly well for the suppressor design are polyethylene, polypropylene, and polycarbonate. Even polymers without a traditional fractional melt can fee sintered with the appropriate pressure and heat, as long as the powders can hind together without melt flow. Examples of polymers in this category are high molecular weight versions of polyethylene that are commercially available. Examples of polymers that work well are listed in the table below, along with relevant material properties. Table 2 is for illustrative purposes only and not meant to fee limiting.

TABLE 2 Polymer and relevant properties. Ticona GUR Sabic Lexan Profax 7823 2122 Property Polycarbonate Polypropylene UHMWPE Unit Standard Density 1.19 0.90 0.93 g/cm³ ASTM D 792/ISO 1183 Melt Flow Rate, 3.50 0.45 <0.1 g/10 min ASTM D 300° C./1.2 kgf 1238 Melt Temperature 320-345 120 130-135 ° C. ° C. ISO 3146 Tensile Stress, yld, Type I, 61.8 27.0 ≧17 MPa ASTM D 50 mm/min 638 Vicat Softening Temp, 154 NR 80 ° C. ASTM D Rate B/50 1525 Heat Deflection 137 88 42 ° C. ASTM D Temperature, 0.45 MPa, 648 6.4 mm, unannealed

Any method known to those skilled in the art of sintering polymer to create the porous micro-channel polymer matrix is contemplated by this disclosure. Annular mold cavities can be used to properly shape and form the matrix. The following is a non-limiting example: A mold for making a tubular matrix can consist of four pieces. An outer tube, two end caps placed at each end of the tube with central apertures, and a rod that runs through these apertures. The rod is centrally located in the outer tube when assembled. The fully assembled tube has a void volume on the inside consistent with the geometry of the porous matrix being produced. The mold is then partially assembled vertically, with the bottom end cap, outer tube and central rod in place. Pellets or powder are poured into the tube while the use of vibration or a packing plunger that settles the pellets and reduce the area between each particle. This allows for a more consistent product. When the mold is filled to the appropriate point, the top end cap is put in place and the assembled mold is ready to be placed into an oven where the particles are sintered at the appropriate temperature and pressure.

The three-dimensional, porous polymer micro-channel diffusion matrix structure in all the embodiments gives the device strength while minimizing density to help drastically reduce weight. In one or more embodiments, the porous microchannel diffusion matrix defines a network of pores having pore diameters in a range of from about 50-400 μm and the diffusion matrix has a porosity in a range of from about 30-60%. Pore diameters can be determined using imaging techniques such as Scanning Electron Microscope imaging. Porosity P can be determined using Equation 1 below, based on the total volume V of the diffusion matrix, including sintered particle volume and pore network volume (can be calculated based on the inner and outer diameters of the diffusion matrix and its length); the material density D of the particles; and the measured mass M of the diffusion matrix. Table 3 below provides the parameters used to determine the porosity of two illustrative diffusion matrixes based on Equation 1.

$\begin{matrix} {P = {\frac{D - \frac{M}{V}}{D}*100}} & {{Equation}\mspace{14mu} 1} \end{matrix}$

TABLE 3 Determination of Porosity of Porous Polymer Matrices Mass Density Outer Diameter Inner Diameter Length Volume Volume Porosity Polymer (g) (g/cc) (in) (in) (in) (in{circumflex over ( )}3) (cc) (%) Polypropylene 5.45 0.9 0.965 0.489 1.111 0.604 9.891 39% Polycarbonate 3.38 1.2 0.989 0.497 0.631 0.362 5.935 53%

The optimal pore size, porosity, outside diameter, inside diameter, length and number of micro-channel layers will vary depending on the caliber of the firearm and the resulting pressurized discharge of the cartridge. Controlling these parameters allows the device to be tailored precisely to each application by altering the porosity and pore size through which the gasses need to pass, thus affecting the resistance. For example, in Table 1, smaller particles yield more effective suppression due to smaller pores that are inevitably created.

The porous polymer micro-channel diffusion matrix effectively reduces the speed of the gases caused by the firearm, discharge. However, to contain the gases within the porous polymer micro-channel diffusion matrix during the diffusing, slowing, and cooling phase, it can be effective to surround the matrix with a sheath. This sheath can be woven, cross-drilled, slotted, or solid in nature. A sheath can increase the efficiency of the suppressor because a sheath forces gases through the entire volume of the porous polymer micro-channel diffusion matrix. Without the sheath, it is possible for the gases to escape the porous polymer micro-channel diffusion matrix to the external environment. While this is not inherently detrimental to the design of the suppressor, it can reduce the efficiency of the suppressor The sheath can be made of any material that can resist temperatures greater than 200F (e.g., metal). Rigid composite materials, such as carbon fiber laminates or carbon fiber/Kevlar composites, work especially well in this regard. In addition, they have the benefit of being durable and lightweight. Of the elastomeric materials that can be used for the sheath, silicone rubber is particularly well suited for this purpose because its durability, thermal resistance, and light weight.

The hollow core tube 5, containment cap 2, and muzzle connection cap 3 can be made from various metals with melting temperatures above 100F. Because these components are the main structural elements, weight, machinability, corrosion resistance, cost, and mechanical strength should also be considered when selecting the metal. Since these components could be exposed to the hot gases created by a firearm discharge, the metal selected should be thermally resistant. Metals that are used to manufacture firearms and firearms attachments typically have these properties, including stainless steel, aluminum, scandium, nickel, chromium, titanium, and alloys of these metals. The hollow core tube serves multiple functions in the suppressor design. The first and most obvious function is to provide a link between the end caps acting as a structural backbone, which in turn connects the suppressor to the firearm. The distal and muzzle end caps make a physical connection to the tube (with threads), the porous micro-channel diffusion polymer matrix floats on the tube and the matrix and the outer sheath are interposed between the end caps. The hollow core tube is what gives the device structure, and aligns the rest of the parts to make a functioning device. The second and most critical function is to vent hot gases produced by the firearm discharge into the porous polymer micro-channel diffusion matrix so that they can be diffused, slowed and cooled. The third function is to provide a clear path for the projectile through the suppressor.

Alternatively, in some embodiments the device, the hollow core tube can be eliminated. The outer sheath would become the structural backbone of the device giving the suppressor structural support and aligning the rest of the device parts. One way to accomplish this is by incorporating an attachment mechanism between the end caps and outer tube. For example, one could use threads that would allow each end cap to be screwed into the corresponding end of the outer sheath. The-porous micro-channel diffusion polymer matrix would then be interposed between the end caps and would slide inside the sheath. Tolerances should be such that when assembled the porous micro-channel diffusion polymer matrix tube is aligned with the apertures in the end caps. This will allow passage of the projectile through the device.

The foregoing description merely illustrates the invention and is not intended to be limiting. It will be apparent to those skilled in the art that various modifications can be made without departing from the inventive concept. Accordingly, it is not intended that the invention be limited except by the appended claims. 

What is claimed is:
 1. A suppressor for use With a firearm configured to fire a round of ammunition including a projectile along a projectile path, the suppressor comprising: a porous micro-channel diffusion polymer matrix having a longitudinal axis, a front end portion and a rear end portion spaced apart along the longitudinal axis, and an interior surface and an exterior surface extending generally along the longitudinal axis, the interior surface defining an internal passage for receiving the projectile through the diffusion polymer matrix; the diffusion polymer matrix being formed of sintered panicles comprising a polymer having a melt flow index of less than about 5 g/10 minutes, the sintered particles being sized and arranged to define pores between adjacent ones of the sintered particles having pore diameters in a range of from about 50 μm to about 400 μm and so that the diffusion polymer matrix has a porosity in a range of from about 30% to about 60%, the pores being fluidly connected to one another to form a network of exhaust flow passages extending through the diffusion polymer matrix from the inferior surface through the exterior surface and from the rear end portion through the front end portion; and a muzzle connector operatively attached to the diffusion polymer matrix configured for mounting the diffusion polymer matrix on a muzzle of the firearm so that the projectile path is aligned with the internal passage of porous micro-channel diffusion polymer matrix.
 2. A suppressor as set forth in claim 1 wherein the polymer has a melt flow index of less than about 3 g/10 minutes.
 3. A suppressor as set forth in claim 2 wherein the polymer has a melt flow index of less than about 1 g/10 minutes.
 4. A suppressor as set forth in claim 1 wherein the polymer comprises one of a polyethylene, a polypropylene, and a polycarbonate.
 5. A suppressor as set forth in claim 1 further comprising a core tube received in the internal passage of the diffusion matrix.
 6. A suppressor as set forth in claim 5 wherein the core tube has a wall and at least one vent hole extending radially through the wall.
 7. A suppressor as set forth in claim 5 further comprising a containment cap secured to the front end portion of the core tube, the muzzle connector being secured to a rear end portion of the core tube and the diffusion matrix extending along the longitudinal axis between the muzzle connecter and the containment cap.
 8. A suppressor as set forth in claim 7 further comprising a sheath the diffusion matrix.
 9. A suppressor as set forth in claim 8 wherein the sheath extends from a rear end portion sealingly engaging the muzzle connector to a front end portion sealingly engaging the containment cap.
 10. A method of making a suppressor, comprising: sintering polymer particles to form a porous diffusion matrix having a longitudinal axis, a rear end portion and a front end portion spaced apart along the longitudinal axis, and an exterior surface extending generally along the longitudinal axis, at least about 90% of the particles by mass having diameters in a range of from about 100 μm to about 3000 μm before said step of sintering; maintaining partial separation between the particles during the step of sintering the particles to define pores between adjacent ones of the particles that are fluidly connected to one another to form a network of exhaust passages extending throughout the diffusion matrix; and forming an internal passage through the diffusion matrix defined by an interior surface of the diffusion matrix opposite the exterior surface, the internal passage extending generally along the longitudinal axis from the rear end portion through the front end portion and being sized and arranged for receiving a projectile through the diffusion matrix, said stop or forming the internal passage including forming openings in the interior surface of the diffusion matrix that fluidly connect the internal passage to the network of exhaust passages.
 11. A method as set forth in claim 11 wherein the diameters of at least about 90% of the particles by mass is in a range of from about 100 μm to about 1000 μm before said step of sintering.
 12. A method as set forth in claim 12 wherein the diameters of at least about 90% of the particles by mass is in a range of from about 100 μm to about 450 μm before said step of sintering.
 13. A method as set forth in claim 11 wherein the particles have a melt flow index of less than about 5 g/10 minutes.
 14. A method as set forth in claim 14 wherein the melt flow index of the particles is less than about 3 g/10 minutes.
 15. A method as set forth in claim 15 wherein the melt flow index of the particles is less than about 1 g/10 minutes.
 16. A method as set forth in claim 11 wherein the particles comprise one of a polyethylene, a polypropylene, and a polycarbonate.
 17. A method as set forth in claim 11 wherein the steps of sintering the particles and forming the internal passage are performed simultaneously.
 18. A method as set forth in claim 18 further comprising positioning the particles in an annular mold cavity.
 19. A method as set forth in claim 19 wherein the step of sintering the particles comprises heating the particles while the particles are positioned in the annular mold cavity.
 20. A method as set forth in claim 11 further comprising securing a muzzle connector configured for being mounted on the muzzle of a firearm to the diffusion matrix.
 21. A method as set forth in claim 21 wherein the step of securing the muzzle connector comprises: securing the muzzle connector to a core tube; inserting the core tube into the internal passage of the diffusion matrix; and securing a containment cap to the core tube so that the diffusion matrix is received over the core tube between the muzzle connector and the containment cap.
 22. A method as set forth in claim 22 further comprising inserting the diffusion matrix into a sheath such that the sheath is received between the muzzle connector and the containment cap.
 23. A method of making a suppressor, comprising; sintering polymer particles having a melt flow index of less than about 5 g/10 minutes to form a porous diffusion matrix having a longitudinal axis, a rear end portion and a front end portion spaced apart along the longitudinal axis, and an exterior surface extending generally along the longitudinal axis; maintaining partial separation between the particles during the step of sintering the particles to define pores between adjacent ones of the particles that are fluidly connected to one another to form a network of exhaust passages extending throughout the diffusion matrix; and forming an internal passage through the diffusion matrix defined by an interior surface of the diffusion matrix opposite the exterior surface, the internal passage extending generally along the longitudinal axis from the rear end portion through the front end portion and being sized and arranged for receiving a projectile through the diffusion matrix, said step or forming the internal passage including forming openings in the interior surface of the diffusion matrix that fluidly couple the internal passage to the network of pores. 